1. Field of the Invention
This invention relates to an improvement in the structure of a liquid-crystal active dot-matrix display and, more particularly, to the spatial configuration of the components of such a display.
2. Description of the Prior Art
As known in the art, a liquid-crystal active display is comprised of liquid-crystal elements, each of which is rendered optically active in response to energization thereof by the operation of its associated field-effect driver-transistor. The driver-transistor, in response to a potential applied to its gate, operates to couple its source to its drain, which, in turn, is coupled to the liquid-crystal element associated with that driver-transistor, thereby energizing the liquid-crystal element. This requires that lines be provided for respectively coupling the source and gate of each driver-transistor to separate points of potential. It is apparent that while the driver-transistors and the lines of such a liquid-crystal active display occupy display area, the display area occupied thereby reduces the display area that can be occupied by the liquid-crystal elements of the display themselves. Thus, the brightness of a liquid-crystal active display is reduced in proportion to the display area not occupied by the liquid-crystal elements, (i.e., amount of the total display area occupied by the driver-transistors, the lines for operating the driver-transistors, etc.).
One known type of liquid-crystal active display structure is a two-dimensional active dot-matrix comprised of an array of pixel (picture element) cells arranged in rows and columns. The active dot-matrix display structure further includes a set of driver-transistor data lines and a set of driver-transistor select lines. A driver-transistor is associated with each individual pixel cell. The respective select lines may correspond with each row and the respective data lines may correspond with each column of the active dot-matrix display, or vice versa. In any event, the source of the driver-transistor associated with each individual pixel cell is coupled to a given coupling location on that data line which energizes that individual pixel cell. Further, the gate of the driver-transistor associated with each individual pixel cell is coupled to the select line which energizes that individual pixel cell.
It is apparent from the above discussion, that the proportion of the display area of a liquid-crystal two-dimensional active dot-matrix display structure occupied by (1) the respective driver-transistors, (2) the respective data lines and (3) the respective select lines increases as the line density of the rows and/or columns increases.
As is known in the art, a liquid-crystal two-dimensional active dot-matrix display structure is usually implemented as an integrated-circuit on a chip. Conventional liquid-crystal two-dimensional active dot-matrix displays generally exhibit a line density in each dimension of the order of 80 lines per inch. In this case, the respective driver-transistors, data lines and select lines occupy only a few percent of the total display area. Thus, the brightness of such a conventional display is limited only to a small extent by the non-optically-active display area occupied by the respective driver-transistors, data lines and select lines of the display. However, the situation is different for a high-density display, such as a display having a density of the order of 1,000 lines per inch in each dimension. The use of the same type of spatial configuration of the display components that is employed for conventional low-density displays would result in the respective optically-active liquid-crystal components of the display occupying only a relatively small (e.g., 30% in the case of 1,000 line per inch display) of the display area, thereby severely reducing the brightness of the display.
As is known, a liquid-crystal element constitutes a capacitance which is shunted by a parasitic capacitance that includes the capacitance of the liquid-crystal-element of each individual pixel cell to the particular data and select lines that are coupled to the driver-transistor associated with that individual pixel cell. This parasitic capacitance, which is undesirable, increases significantly as the line density of the display increases.
The present invention is directed to a new spatial configuration of the components of a liquid-crystal two-dimensional active dot-matrix display structure that (1) permits the proportion of the total display area occupied by the respective-crystal elements of a relatively high-density active dot-matrix display to be significantly increased, and (2) significantly reduces the undesirable parasitic capacitance normally exhibited by such a high-density active dot-matrix display.